The present invention relates to an effect adding method and an effect adding apparatus, which are capable of emphasizing rich sounds, extension and gorgeousness of a high tone range, and powerful feelings of low tones in audio reproducing operations. More specifically, the present invention relates to such effect adding method and apparatus, which are applied to a reproducing operation of sound sources having high compression ratios so as to achieve an excellent sound effect.
Generally speaking, in compressed audio format sound sources known as MP3 (MPEG-1 Audio Layer III), AAC (Advanced Audio Coding of MPEG-2/4 Audio), and the like, components in a high tone range and such components which can be hardly heard in view of an acoustic psychological aspect are removed away during encoding operation in order to realize a high compression ratio. For instance, in the case of MP3, signal components higher than, or equal to 16 KHz are cut when the most utilized compression ratio (128 Kbps) is selected. As a result, sounds of compressed sound sources may be heard as follows: That is, sounds in high tone ranges may be heard as dull or dim sounds, or may be heard as lean sounds without dynamism and vitality in an entire component.
Recently, as technical ideas for reinforcing high tone ranges when sound sources such as CDs whose ranges have been limited are played back, there is a technical idea described in Japanese Patent No. 3137289 (FIG. 1). This technical idea is made as follows: That is, higher harmonic components of a sound source are produced based upon the sound source whose range has been limited, the produced higher harmonic components are added to the sound source whose range has been limited, and the resulting sound source is played back, so that the sounds in the sound ranges covering such a sound range higher than that of the sound source whose range has been limited can be played back.
However, as to the sound sources such as MP3 and AAC having the high compression ratios, the rich sounds and the dynamism and vitality of low tones cannot be obtained by merely reinforcing the above-explained high tone range, so that the effect for improving the sound qualities is still insufficient.